Re: [patch 10/21] buffer heads: Support slab defrag

David Chinner
2008-05-12T00:24:44Z

On Fri, May 09, 2008 at 08:08:41PM -0700, Christoph Lameter wrote:
> Defragmentation support for buffer heads. We convert the references to
> buffers to struct page references and try to remove the buffers from
> those pages. If the pages are dirty then trigger writeout so that the
> buffer heads can be removed later.

Oh, no, please don't trigger more random single page writeback from
memory reclaim. We shoul dbe killing the VM's use of ->writepage,
not encouraging it.

If you are going to clean bufferheads (or pages), please clean entire
mappings via ->writepages as it leads to far superior I/O patterns
and a far higher aggregate rate of page cleaning.....

Cheers,

Dave.
--
Dave Chinner
Principal Engineer
SGI Australian Software Group